Scrubber wash water not harmful to environment, finds study

Scrubber wash water not harmful to environment, finds study
Poul Woodall, director, Environment & Sustainability, DFDS, and CSA 2020 executive committee member

The Clean Shipping Alliance (CSA) 2020 has welcomed the preliminary results of an independent study presented by Dutch research organisation CE Delft, that indicates accumulated concentrations of exhaust gas cleaning systems (EGCS, or “scrubbers”) wash water components are at very low levels and well below applicable regulatory limits.

The study, presented to international delegates of the 74th session of IMO’s Marine Environment Protection Committee (MEPC) on May 14 in London, will help inform the current debate regarding the environmental impact of open-loop scrubbers on the marine environment, and particularly on ports and harbours.

Along with a similar study conducted by Japan’s Transport Ministry, it is expected that the CE Delft research, will help fill important gaps in the scientific record.

The research carried out by CE Delft in collaboration with Deltares, an independent institute for applied research in the Netherlands, uses three versions of Deltares’ state-of-the-art dynamic computer modelling system MAMPEC. Each version represents a common configuration of European ports, and the study assumes that multiple ships in each modelled port are using open-loop scrubbers around the clock throughout the year.

Sponsored by CLIA Europe and Interferry, the ongoing study is assessing the accumulated impact of exhaust gas cleaning systems on the water quality in various common port configurations by evaluating the concentration of nine metals and 16 polycyclic aromatic hydrocarbons (PAH).

CE Delft researchers used wash water samples taken from the scrubber tower outlet of cruise ships, bulk carriers and ferries prior to any buffering or other wash water after-treatment processes.

In the first model, the researchers found that “for most of the compounds considered in the specified reference scenario and not considering wash water after-treatment, multiple ships using open-loop EGCSs may increase the equilibrium concentration in the port by 0 per cent -0.01 per cent of the annual average new Environmental Quality Standard expected to go into force in the EU in 2021, as part of a new Water Framework Directive”.

Only in their assessment of concentrations of Naphthalene, Nickel, Benzo(a)pyrene, and Fluoranthene did the researchers find a slight increase in the equilibrium concentrations, though still only between 0.02 per cent and 0.2 per cent of the maximum annual average Environmental Quality Standard specified for 2021.

“So far, for all parameters considered, the equilibrium concentrations are indicating annualised contributions on the parts per trillion scale, which we understand are actually too small to be detected by existing laboratory equipment. This is an encouraging start,” said CSA 2020 executive committee member Poul Woodall, director, Environment & Sustainability, DFDS,

According to the study’s sponsors, CE Delft will continue to assess the accumulated concentration of scrubber discharge water compounds in two more port configurations and compare the resulting concentrations against other standards. It will also compare the compound concentrations being discharged from ships in port with the background concentrations provided to ports by other sources, such as rivers.

CSA 2020 executive committee member Arne Hubregtse, executive board member of Spliethoff Group, observed: “These initial findings are very promising and suggest that those ships operating open-loop EGCS will have near zero impact on the quality of harbour waters.”

Ian Adams, executive director, CSA 2020, added: “Many of the those attending MEPC 74 recently will have heard these preliminary results from the CE Delft study, which appear to be building on the scientific evidence showing no environmental impact to the marine environment from ships using exhaust gas cleaning systems to meet IMO 2020 guidelines.

“While there is no debate surrounding the technology’s air emissions-busting capability, we hope that the CE Delft study, along with other recently published scientific research, will help answer remaining questions surrounding the environmental impact of scrubber wash water.”

CE Delft expects to complete and publish the full study this summer.